Plasticity-induced Hydrogen Desorptions Associated with Hydrogen-assisted Martensitic Transformation and Deformation Twinning in Austenitic Stainless Steels

The hydrogen desorption behaviors of the SUS304 and SUS316L austenitic stainless steels during deformation at ambient temperature were investigated using a tensile test machine in a vacuum chamber equipped with a mass spectrometer. Obvious hydrogen desorption was detected only in the SUS304 steel, which exhibited a distinct martensitic transformation. Because the hydrogen desorption rate in SUS304 decreased when deformation stopped, a significant factor causing transformation-induced hydrogen desorption was an increase in martensite fraction during plastic deformation. Furthermore, hydrogen promoted both martensitic transformations to ε and to α′, which assists the hydrogen desorption. These results indicate the presence of synergistic interactions between the hydrogen uptake/diffusion and martensitic transformation. In contrast, SUS316L steel showed no martensitic transformation and exhibited hydrogen-assisted deformation twinning. No significant increase in hydrogen desorption was observed during plastic deformation. This result indicates that deformation twinning has no effect on hydrogen diffusion/desorption.